The size of your prediction bar is determined by your keyboard size. So if you want to make it bigger you'll need to change the size of your keyboard. To do this:
- Open the SwiftKey Hub
- Tap 'Resize'
- Choose your desired size
You can also resize your keyboard from within SwiftKey settings in the following way:
- Open the SwiftKey app
- Tap 'Typing'
- Tap 'Keys'
- 'Resize keyboard' option will be at the top